Which of the following pairs of hydrate name and chemical formula is correctly matched?

• A. Calcium sulfate dihydrate, CaSO4 · H2O
• B. Copper(II) sulfate pentahydrate, CuSO4 · 5H2O
• C. Sodium carbonate monohydrate, Na2CO3 · 2H2O
• D. Magnesium chloride trihydrate, MgCl2 · 2H2O

Answer: (B)

Verified step by step guidance

1. Understand that hydrates are compounds that include a specific number of water molecules attached to their formula unit, indicated by a dot followed by the number of water molecules (e.g., \( \cdot 5H_2O \) means five water molecules).
2. Recall the correct chemical formulas for common hydrates: for example, calcium sulfate dihydrate is \( \text{CaSO}_4 \cdot 2H_2O \), copper(II) sulfate pentahydrate is \( \text{CuSO}_4 \cdot 5H_2O \), sodium carbonate decahydrate is \( \text{Na}_2\text{CO}_3 \cdot 10H_2O \), and magnesium chloride hexahydrate is \( \text{MgCl}_2 \cdot 6H_2O \).
3. Compare each given name and formula pair to these known correct formulas to check if the number of water molecules matches the hydrate name (e.g., 'dihydrate' means 2 water molecules, 'pentahydrate' means 5, 'monohydrate' means 1, 'trihydrate' means 3).
4. Identify any mismatches where the hydrate name's prefix does not correspond to the number of water molecules in the formula (for example, if 'dihydrate' is paired with only 1 water molecule, it is incorrect).
5. Conclude which pair is correctly matched by confirming that both the chemical formula and the hydrate name agree on the number of water molecules.